Java Community | Help. Code. Learn.•2mo ago

Week 94 — How can one convert a datetime from one timezone to another?

Question of the Week #94

How can one convert a datetime from one timezone to another?

5 Replies

LocalDateTimes which are used for representing datetimes don't have any information about the timezone of a given datetime. To add timezone information to a LocalDateTime, the atZone() method can be used with a ZoneId argument obtaining a ZonedDateTime.

LocalDateTime currentDateTime = LocalDateTime.now();
ZonedDateTime currentDateTimeWithTimezone = currentDateTime.atZone(ZoneId.systemDefault());//use the timezone configured on the current system

LocalDateTime currentDateTime = LocalDateTime.now();
ZonedDateTime currentDateTimeWithTimezone = currentDateTime.atZone(ZoneId.systemDefault());//use the timezone configured on the current system

ZonedDateTime is then able to convert from one timezone to another using the withZoneSameInstant method that also takes a ZoneId argument which represents the timezone to convert to. After that, it can be converted to a LocalDateTime using the toLocalDateTime() method:

ZonedDateTime currentDateTimeInUTC = currentDateTimeWithTimezone.withZoneSameInstant(ZoneId.of("UTC"));//convert to UTC
LocalDateTime currentDateTimeOfUTCWithoutTimezoneInformation = currentDateTimeInUTC.toLocalDateTime();
System.out.println("The current datetime in UTC is " + currentDateTimeOfUTCWithoutTimezoneInformation);

ZonedDateTime currentDateTimeInUTC = currentDateTimeWithTimezone.withZoneSameInstant(ZoneId.of("UTC"));//convert to UTC
LocalDateTime currentDateTimeOfUTCWithoutTimezoneInformation = currentDateTimeInUTC.toLocalDateTime();
System.out.println("The current datetime in UTC is " + currentDateTimeOfUTCWithoutTimezoneInformation);

📖 Sample answer from dan1st

Eric McIntyre•2mo ago

ZoneId originalZone = ZoneId.of("America/New_York"); ZoneId targetZone = ZoneId.of("Europe/London"); ZonedDateTime originalDateTime = ZonedDateTime.now(originalZone); ZonedDateTime convertedDateTime = originalDateTime.withZoneSameInstant(targetZone);

Eric McIntyre•2mo ago

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss z");

Submission from coojak5585

Eric McIntyre•2mo ago

I would create or have a created ZonedDateTime with the original timezone,then I’d have to use withZoneSameInstant() & put a ZoneId with the new time zone between its parenthesis . I also would to have to add to the instants that were in and around the original time zone code/lines , adding “In” with the new time zone directly with the “instant” typed after ZoneDateTime for the new line & new time zone code . The line would read ZoneDateTime instantInET . It would be another “instantInET” with system.out.println() to print/display . The last instant used will be before “instant.” together typed in front of “with.ZoneSameInstant “ to look like this after the the equal sign instant.with.ZoneSameInstant(). Within the ZoneSameInstant parentheses there would the typed “ ZoneId.of.(“ET”)); “ with the new time in it

Submission from miamason

Eric McIntyre•2mo ago

To convert time between time zones in Java, use the ZonedDateTime and ZoneId classes from the java.time package: 1.Create a ZonedDateTime object in the source time zone. 2.Use the withZoneSameInstant() method to convert it to the target time zone. Example: ZoneId sourceZone = ZoneId.of("America/New_York"); ZoneId targetZone = ZoneId.of("Asia/Kolkata"); ZonedDateTime sourceTime = ZonedDateTime.now(sourceZone); ZonedDateTime targetTime = sourceTime.withZoneSameInstant(targetZone);

Submission from harshtarsariya

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Week 94 — How can one convert a datetime from one timezone to another?